Permissions note for merging tool (#60)

docs/en/manuals/extensions-manifest-merge-tool.md

@@ -33,6 +33,8 @@ The extension manifests must be placed in a certain structure for the extension
 The Android platform already has a manifest merging tool (based on `ManifestMerger2`), and we use it inside `bob.jar` to merge manifests.
 For a complete set of instructions on how to modify your Android manifests, please refer to [their documentation](https://developer.android.com/studio/build/manifest-merge)
 
+> If you don't set your app's `android:minSdkVersion='9'` in your extension manifest, the following permissions will be added automatically:  `WRITE_EXTERNAL_STORAGE`, `READ_PHONE_STATE`, `READ_EXTERNAL_STORAGE`.
+
 ### Example
 
 Base manifest
@@ -54,6 +56,7 @@ Extension manifest:
 
     <?xml version='1.0' encoding='utf-8'?>
     <manifest xmlns:android='http://schemas.android.com/apk/res/android' package='com.defold.testmerge'>
+        <uses-sdk android:minSdkVersion='9' />
         <uses-feature android:required='true' android:glEsVersion='0x00030000' />
         <application>
             <meta-data android:name='com.facebook.sdk.ApplicationName'
@@ -80,9 +83,6 @@ Result
         <uses-feature
             android:glEsVersion='0x00030000'
             android:required='true' />
-        <uses-permission android:name='android.permission.WRITE_EXTERNAL_STORAGE' />
-        <uses-permission android:name='android.permission.READ_PHONE_STATE' />
-        <uses-permission android:name='android.permission.READ_EXTERNAL_STORAGE' />
         <application
             android:hasCode='true'
             android:label='Test Project' >